Compared to the rest of the San Diego market, the Rancho Santa Fe region has greater rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 0 listings have been made available, which means office spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About Inf% of the listings in the Rancho Santa Fe are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 780 sqft. Most properties in this market are around 2 stories. Most buildings in this area were built in 1989 and are Class B.